JP5040160B2 - Inverter controller for motor drive - Google Patents

Description

  The present invention relates to a motor drive inverter control device using a small capacity reactor and a small capacity capacitor.

  As a general motor drive inverter control device used in a general-purpose inverter or the like, a motor drive inverter control device as shown in FIG. 7 is well known.

  In FIG. 7, the main circuit is composed of a DC power supply device 113, an inverter 2 and a motor 3. The DC power supply device 113 is used for the AC power supply 1, the rectifier circuit 7 and the DC voltage source of the inverter 2. Are composed of a smoothing capacitor 112 for storing electrical energy and a power factor improving reactor 111 of the AC power source 1.

  On the other hand, in the control calculation unit, the voltage command calculation unit 9 that creates each phase voltage command value of the motor 3 based on the speed command of the motor 3 given from the outside, and each phase voltage created by the voltage command calculation unit 9 The base driver 10 is configured to perform PWM control of the inverter 2 based on the command value.

  Here, when the AC power source 1 is 220 V (power frequency 50 Hz), the input of the inverter 2 is 1.5 kW, and the smoothing capacitor 112 is 1500 μF, the harmonic component of the power source current when the power factor improving reactor 111 is 5 mH and 20 mH. FIG. 8 shows the relationship between the power and the order with respect to the power supply frequency.

  FIG. 8 is shown together with the IEC (International Electrotechnical Commission) standard. When the power factor improving reactor 111 is 5 mH, the third harmonic component greatly exceeds that of the IEC standard. In the case of, it is understood that the IEC standard is cleared in the harmonic components up to the 40th order.

  For this reason, it is necessary to take measures such as further increasing the inductance value of the power factor improving reactor 111 in order to clear the IEC standard even when the load is high, increasing the size and weight of the inverter device, and further increasing the cost. There was an inconvenience of inviting.

  Therefore, a DC power supply device as shown in FIG. 9 has been proposed as a DC power supply device that suppresses an increase in inductance value of the power factor improving reactor 111 and achieves a reduction in power harmonic components and an increase in power factor ( For example, see Patent Document 1).

  In FIG. 9, the power supply voltage of the AC power supply 1 is applied to the AC input terminal of the full-wave rectifier circuit formed by bridge-connecting the diodes D1 to D4, and the output is charged to the intermediate capacitor C via the reactor Lin. The electric charge of the intermediate capacitor C is discharged to the smoothing capacitor CD, and a DC voltage is supplied to the load resistor RL.

  In this case, the transistor Q1 is connected to the positive and negative DC current path connecting the load side of the reactor Lin and the intermediate capacitor C, and the transistor Q1 is driven by the base drive circuit G1.

The circuit further includes pulse generation circuits I1 and I2 that apply a pulse voltage to the base drive circuit G1, and a dummy resistor Rdm. The pulse generation circuits I1 and I2 each detect a zero-cross point of the power supply voltage; A pulse current circuit that allows a pulse current to flow through the dummy resistor Rdm until the instantaneous value of the power supply voltage becomes equal to the voltage across the intermediate capacitor C from the detection of the zero cross point.

  Here, the pulse generation circuit I1 generates a pulse voltage in the first half of the half cycle of the power supply voltage, and the pulse generation I2 generates a pulse voltage in the second half of the half cycle of the power supply voltage.

  When the transistor Q1 is turned on and a current is forced to flow through the reactor Lin, a backflow prevention diode D5 is connected so that the charge of the intermediate capacitor C is not discharged through the transistor Q1, and further, the intermediate capacitor C A backflow prevention diode D6 and a reactor Ldc for enhancing the smoothing effect are connected in series to a path for discharging the electric charge of the current to the smoothing capacitor CD.

With the above configuration, by turning on the transistor Q1 in part or all of the phase interval in which the instantaneous value of the power supply voltage does not exceed the voltage across the intermediate capacitor C, harmonic components can be maintained while suppressing the increase in size of the device. Reduction and higher power factor can be achieved.
JP-A-9-266684

  However, the above-described conventional configuration still has the smoothing capacitor CD having a large capacity and the reactor Lin (described in the simulation result at 1500 μF and 6.2 mH in Patent Document 1), and further the intermediate capacitor. C, transistor Q1, base drive circuit G1, pulse generation circuits I1 and I2, dummy resistor Rdm, backflow prevention diodes D5 and D6, and a reactor Ldc that enhances the smoothing effect, thereby increasing the size of the device and the number of parts. There was a problem of incurring a cost increase accompanying the increase.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a small, lightweight, and low-cost motor drive inverter control device that suppresses harmonic components of a power supply current.

In order to solve the above-mentioned problems, an inverter control apparatus for driving a motor according to the present invention comprises an AC power supply as an input and a diode bridge and a very small capacity reactor connected to the AC input side or DC output side of the diode bridge. Rectifier circuit, inverter for converting DC power to AC power, a motor, a control calculation unit for controlling the operation of the inverter, an inverter input voltage detection unit for detecting an applied voltage value of the inverter, and the inverter And an extremely small-capacitance capacitor between the buses, and in the control calculation unit, the inverter applied voltage phase is calculated from the applied voltage value of the inverter detected by the inverter input voltage detection unit, and the inverter applied voltage phase is calculated. voltage command value applied to the motor is derived by using the motor phase electric Waveforms improved voltage in each phase in order to eliminate the distortion of the group phase information obtained from the inverter application voltage phase calculation section adds to the motor command voltage is characterized in that is performed only in a predetermined period.

  As a result, a small, lightweight, and low cost motor drive inverter control device is realized by using a small-capacitor and a small-capacity reactor, and the motor applied voltage is derived using the inverter applied voltage phase. Power factor improvement and harmonic countermeasures.

The motor drive inverter control device of the present invention can realize a motor drive inverter control device that is small, light, and low cost by using a small-capacity reactor and a small-capacitance capacitor, and can easily improve the power factor of the power source current. The system reliability can be improved.

According to a first aspect of the present invention, there is provided a motor drive inverter control device including an AC power supply as an input, a rectifier circuit including a diode bridge and an extremely small capacity reactor connected to an AC input side or a DC output side of the diode bridge. An inverter that converts DC power to AC power, a motor, a control calculation unit that controls the operation of the inverter, an inverter input voltage detection unit that detects an applied voltage value of the inverter, and a bus between the inverters A small-capacitance capacitor, and the control calculation unit calculates an inverter applied voltage phase from an applied voltage value of the inverter detected by the inverter input voltage detection unit, and uses the inverter applied voltage phase for the motor. voltage command value to be applied is derived, in order to eliminate the distortion of the motor phase current By waveforms improved voltage in phase addition of the motor command voltage is performed only in a predetermined period based on the phase information obtained from the inverter application voltage phase calculation section, the distortion of the AC power supply current waveform can be reduced, size and weight -A motor drive inverter control device that is low in cost but high in power factor can be realized.

  The inverter control apparatus for driving a motor according to a second aspect of the invention is particularly the first aspect of the invention, wherein the inverter applied voltage phase is such that the applied voltage value of the inverter detected by the inverter input voltage detector is equal to or greater than a threshold value. In addition, by setting the interval of the change timing from the increase to the decrease as one cycle, the inverter applied voltage phase can be accurately calculated even when the motor type or the operating condition is changed.

  According to a third aspect of the present invention, there is provided an inverter control apparatus for driving a motor, particularly in the second aspect, wherein the threshold value is variable in accordance with an applied voltage value of the inverter while the motor is stopped. The inverter applied voltage phase can be automatically calculated at any voltage.

  The inverter control device for driving a motor according to a fourth aspect of the invention, particularly in the first to third aspects of the invention, so that the resonance frequency of the small-capacity reactor and the small-capacitance capacitor is greater than 40 times the power supply frequency. By determining the combination of the small-capacity reactor and the small-capacitance capacitor, the harmonic component of the power supply current can be suppressed and the IEC standard can be cleared.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a system configuration diagram of a motor drive inverter control apparatus showing a first embodiment of the present invention. The motor drive inverter control device includes an AC power source 1, a diode bridge 7 that converts AC power into DC power, a small capacity reactor 11 of 2 mH or less, a small capacity capacitor 12 of 0.4 μF to 100 μF, and a drive that is supplied to the brushless motor 3. An inverter 2 that generates and outputs a voltage and a control unit 6 that controls the inverter 2 are included.

  The brushless motor 3 includes a stator 4 to which three-phase windings 4u, 4v, 4w Y-connected around a neutral point are attached, and a rotor 5 to which a magnet is attached.

  The U-phase terminal 8u is connected to the non-connected end of the U-phase winding 4u, the V-phase terminal 8v is connected to the non-connected end of the V-phase winding 4v, and the W-phase terminal 8w is connected to the non-connected end of the W-phase winding 4w. Yes.

The inverter 2 has a half-bridge circuit composed of a pair of switching elements for three phases for U phase, V phase, and W phase. A pair of switching elements of the half-bridge circuit are connected in series between the high-voltage side end and the low-voltage side end of the small-capacitance capacitor 12, and a DC voltage is applied to the half-bridge circuit. The U-phase half-bridge circuit includes a switching element 13u on the high voltage side (upper arm) and a switching element 13x on the low voltage side (lower arm). The V-phase half-bridge circuit includes a high-voltage side switching element 13v and a low-voltage side switching element 13y. The W-phase half-bridge circuit includes a high-voltage side switching element 13w and a low-voltage side switching element 13z.

  In addition, free wheel diodes 14u, 14v, 14w, 14x, 14y, and 14z are connected in parallel with the switching elements. The terminals 8u, 8v, and 8w of the brushless motor 3 are connected to the interconnection point between the switching element 13u and the switching element 13x in the inverter 2, the interconnection point between the switching element 13v and the switching element 13y, and the interconnection point between the switching element 13w and the switching element 13z. Each is connected.

  The DC voltage applied to the inverter 2 is converted into a three-phase AC voltage by the switching operation of the switching element in the inverter 2 described above, whereby the brushless motor 3 is driven.

  Further, current sensors 15v and 15w for detecting a phase current are disposed between the inverter 2 and the brushless motor 3.

  The control unit 6 includes a voltage command calculation unit 9, a base driver 10, a motor phase estimation unit 17, a rotor speed detection unit 18, a current command calculation unit 19, and an inverter applied voltage phase calculation unit 20.

  The motor phase estimator 17 uses the phase current of the brushless motor 3 from the information obtained by the current sensors 15v and 15w, the output voltage calculated by the voltage command calculator 9, and the inverter 2 detected by the inverter input voltage detector 16. The phase of the brushless motor 3 is estimated from information on the voltage applied to the brushless motor 3.

  Further, the rotor speed detector 18 estimates the speed of the brushless motor 3 from the estimated phase.

  Based on deviation information between the estimated speed of the rotor 5 and the target speed given from the outside, the current command calculation unit 19 performs PI calculation on the current command execution value to be energized so that the rotor speed becomes the target speed. The voltage command calculation unit 9 calculates the output voltage applied to the brushless motor 3.

  The output voltage information is output to the base driver 10, and the switching elements 13u, 13v, 13w, 13x, 13y, and 13z are PWM-controlled to generate a sinusoidal alternating current.

  As described above, in this embodiment, the sinusoidal drive of the brushless motor 3 is realized by passing a sinusoidal phase current.

  FIG. 2 shows the first operation result of the motor drive inverter control device of the present invention. Since the capacitor 12 of the present invention uses an extremely small capacity, the inverter applied voltage is the power supply frequency fs (= 50 Hz). It can be seen that there is a large pulsation at a frequency twice that of).

  Regarding the power supply current, since the capacitor 12 has a small capacity and the charge / discharge time is extremely short, there is almost no current pause period and a high power factor is realized.

  FIG. 3 shows a second operation result of the motor drive inverter control apparatus according to the present invention, and shows a waveform when a 6-pole three-phase motor is driven at 4000 rpm at a power supply frequency of 50 Hz.

  When the power supply current is observed in more detail here, a pulsation with a period T1 larger than the carrier component of the inverter 2 appears. Looking at the relationship between the pulsation of the power supply current and the phase current of the brushless motor 3, an arrow indicates It can be seen that the distorted portion of the motor phase current shown matches the power supply current drop timing.

  The main cause of the distortion of the motor phase current is due to incomplete turn-on of the freewheeling diode connected in reverse parallel to the switching element during the dead time period provided for preventing the short circuit of the upper and lower arms of the inverter 2. As a result, the output voltage becomes discontinuous near the zero cross point of the motor phase current, and appears as distortion of the motor phase current.

  In the inverter control apparatus for driving a motor according to the present invention, an extremely small capacity reactor and capacitor are used, so that the above-described distortion of the motor phase current tends to appear as a pulsation of the power supply current.

  Next, consider the harmonic regulation of power supply current.

  The harmonic current indicates a current having a frequency component that is an integral multiple of the sinusoidal waveform of the AC power supply 1. In electronic equipment, a regulation value is provided for the harmonic current.

  If the pulsation of the power source current described so far has a frequency that is an integral multiple of the sine wave waveform of the AC power source 1, the regulation value may not be satisfied.

Therefore, in order to eliminate the above-described distortion of the motor phase current, the voltage command calculation unit 9 converts the waveform improvement voltages v _ud ^* , v _vd ^* , v _wd ^* in each phase into motor command voltages v _uh ^* , v _vh ^* , v _By adding to _wh ^* , the distortion of the motor phase current near the zero cross point is suppressed, and the pulsation of the power supply current is suppressed.

The voltage command values V _u ^* , V _v ^* , and V _w ^* output from the voltage command calculation unit 9 are expressed by Equation 1.

  FIG. 4 shows the third operation result of the motor drive inverter control apparatus of the present invention.

As for the waveforms, the center shows the power supply current and the lower side shows the motor phase current, and both are operating as a result of adding the waveform improvement voltages v _ud ^* , v _vd ^* , and v _wd ^* .

  Compared with the operation result shown in FIG. 3, it can be seen that the pulsation of the power source current, that is, the generation of the harmonic current is suppressed by reducing the distortion near the zero cross point of the motor phase current.

  In the inverter applied voltage phase calculation unit 20, the period (inverter) is greatly pulsating at a frequency twice the power supply frequency fs (= 50 Hz) based on the information of the voltage applied to the inverter 2 detected by the inverter input voltage detection unit 16. (Applied voltage phase) is calculated.

In the waveform shown in FIG. 4, the addition of the waveform improvement voltages v _ud ^* , v _vd ^* , v _wd ^* in each phase to the motor command voltages v _uh ^* , v _vh ^* , v _wh ^* is an inverter applied voltage phase calculation unit. Based on the phase information obtained from 20, it is performed only in the period T2, and the waveform distortion is suppressed at an appropriate timing.

(Embodiment 2)
In the second embodiment of the present invention, in the motor drive inverter control device of the first embodiment, the applied voltage value of the inverter 2 detected by the inverter input voltage detection unit 16 is equal to or greater than a threshold value and decreases from an increase. The inverter application voltage phase calculation unit 20 performs the calculation with this interval as one period of the inverter application voltage phase.

  FIG. 5 shows a fourth operation result of the inverter control apparatus for driving a motor according to the present invention, which is a result calculated by the power supply voltage of 200 V, the inverter applied voltage, and the inverter applied voltage phase calculation unit 20.

  As shown in FIG. 2, the voltage applied to the inverter is greatly pulsated at a frequency twice as high as the power supply frequency fs (= 50 Hz), but at the zero cross timing of the power supply voltage (a circled portion) Yes.

  This is the regenerative voltage of the brushless motor 3, and its magnitude varies depending on the specification of the induced voltage.

  When the inverter applied voltage phase calculation unit 20 derives one cycle of the inverter applied voltage phase, if only the inflection point of the inverter applied voltage is recognized, the above-described regenerative voltage influences and the inverter applied voltage phase is erroneously recognized. However, it is possible to obtain an accurate calculation result by adding a judgment based on a threshold value.

(Embodiment 3)
In the third embodiment of the present invention, in the motor drive inverter control apparatus of the second embodiment, the threshold value used in the inverter applied voltage phase calculation unit 20 is set to the applied voltage value of the inverter 2 when the brushless motor 3 is stopped. It was made variable accordingly.

  FIG. 6 shows a fifth operation result of the motor drive inverter control apparatus according to the present invention, showing a power supply voltage of 200 V and an inverter applied voltage when the brushless motor 3 is stopped.

  When the brushless motor 3 is stopped, almost no power supply current flows, and the pulsation of the inverter applied voltage as shown in FIGS. 2 and 5 does not appear.

  By setting a threshold value used by the inverter applied voltage phase calculation unit 20 to a value lower by several V to several tens V from the inverter applied voltage in this state, an accurate inverter applied voltage phase is calculated regardless of the power supply voltage. It became possible.

  In particular, assuming a case in Japan, the motor drive inverter control device of the present invention can be used regardless of whether the commercial power supply voltage is 100V or 200V.

(Embodiment 4)
A specific method for determining the specifications of the small-capacity capacitor and small-capacity reactor according to the present invention will be described below.

In the motor drive inverter control device of the present invention, the resonance frequency f _LC (LC resonance frequency) of the small capacitor and the small reactor is set to the power frequency in order to suppress the harmonic component of the power current and clear the IEC standard. The combination of the small capacitor and the small reactor is determined so as to be larger than 40 times fs.

Here, when the capacitance of the small-capacitance capacitor is C [F] and the inductance value of the small-capacity reactor is L [H], the LC resonance frequency f _LC is expressed by Equation 2.

That is, the combination of the small capacitor and the small reactor is determined so as to satisfy f _LC > 40 fs. (Because the IEC standard specifies the 40th harmonic in the harmonic component of the power supply current)
As described above, by determining the combination of the small-capacity capacitor and the small-capacity reactor, the harmonic component of the power supply current can be suppressed and the IEC standard can be cleared.

  Note that the present invention described in the first to fourth embodiments can be applied to a motor drive inverter control device that drives a motor using an inverter circuit.

  For example, an air conditioner equipped with an inverter circuit, a refrigerator, an electric washing machine, an electric dryer, an electric vacuum cleaner, a blower, a heat pump water heater and the like.

  For any product, by reducing the size and weight of the motor drive inverter device, the degree of freedom in product design is improved, and an inexpensive product can be provided.

  As described above, the motor drive inverter control device according to the present invention can realize a small, light, and low cost motor drive inverter control device by using a small-capacity reactor and a small-capacitance capacitor. High power factor operation with suppressed components is possible and system reliability can be improved, so only when speed sensors such as pulse generators cannot be used, such as compressor drive motors in air conditioners The present invention can also be applied to a case where a speed sensor can be provided, such as a servo drive.

1 is a system configuration diagram of an inverter control device for driving a motor showing a first embodiment of the present invention. The figure which shows the 1st operation result in the embodiment The figure which shows the 2nd operation result in the embodiment The figure which shows the 3rd operation result in the same embodiment The figure which shows the 4th operation result in the 2nd Embodiment of this invention. The figure which shows the 5th operation result in the 3rd Embodiment of this invention. System configuration diagram of a general motor drive inverter control device The diagram which showed the relationship between the harmonic component of the power supply current in the motor drive inverter apparatus of FIG. 10, and the order with respect to a power supply frequency Configuration diagram of a conventional DC power supply that can reduce harmonic components and achieve a high power factor while suppressing the increase in size of the device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Inverter 3 Brushless motor 4 Stator 4u, 4v, 4w Winding 5 Rotor 6 Control part 7 Diode bridge 8u, 8v, 8w Terminal 9 Voltage command calculating part 10 Base driver 11 Small capacity reactor 12 Small capacity capacitor 13u , 13v, 13w Upper arm switching element 13x, 13y, 13z Lower arm switching element 14u, 14v, 14w, 14x, 14y, 14z Free wheel diode 15v, 15w Current sensor 16 Inverter input voltage detection unit 17 Motor phase estimation unit 18 Rotor Speed detector 19 Current command calculator 20 Power supply frequency calculator 111 Reactor 112 Smoothing capacitor 113 DC power supply

Claims (4)

A rectifier circuit including an AC power supply as an input, a diode bridge and a very small capacity reactor connected to the AC input side or DC output side of the diode bridge, an inverter for converting DC power to AC power, and a motor A control operation unit that controls the operation of the inverter, an inverter input voltage detection unit that detects an applied voltage value of the inverter, and a very small capacitor between the buses of the inverter, the together from the application voltage value of the inverter to be detected by the inverter input voltage detection unit calculates an inverter application voltage phase, the voltage command value applied to the motor using the inverter application voltage phase is derived, the motor phase current The waveform improvement voltage in each phase is added to the motor command voltage to eliminate distortion. There motor drive inverter control apparatus characterized by being carried out only in a predetermined period based on the phase information obtained from the inverter application voltage phase calculation section. The inverter applied voltage phase is characterized in that the applied voltage value of the inverter detected by the inverter input voltage detector is equal to or greater than a threshold value, and the timing interval at which the inverter changes from increasing to decreasing is defined as one cycle. The inverter control device for driving a motor according to claim 1. 3. The motor drive inverter control device according to claim 2, wherein the threshold value is variable according to an applied voltage value of the inverter while the motor is stopped. The combination of the small-capacity reactor and the small-capacitance capacitor is determined so that the resonance frequency of the small-capacity reactor and the small-capacitance capacitor is larger than 40 times the power supply frequency. 4. The motor drive inverter control device according to claim 3.

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